chore: update validator nonces in endblocker (#1292)

# Related Github tickets

- VolumeFi#2160

# Background

The way it was before, we would need a claim to be observed so
validators would be updated. By doing it in the endblocker, we
validators are always up-to-date.

This should prevent a situation where the last claim is 19, the last
observed nonce is 18, but validators are stuck on nonce 17. They would
receive a list of block events with the block of nonce 19 (latest
unobserved) but would be unable to claim it, since skyway would expect
them to submit a claim for nonce 18 instead.

# Testing completed

- [ ] test coverage exists or has been added/updated
- [x] tested in a private testnet

# Breaking changes

- [x] I have checked my code for breaking changes
- [x] If there are breaking changes, there is a supporting migration.

x/skyway/abci.go

@@ -14,8 +14,12 @@ import (
 	"github.com/palomachain/paloma/x/skyway/types"
 )
 
+const updateValidatorNoncesPeriod = 50
+
 // EndBlocker is called at the end of every block
 func EndBlocker(ctx context.Context, k keeper.Keeper, cc *libcons.ConsensusChecker) {
+	sdkCtx := sdk.UnwrapSDKContext(ctx)
+
 	logger := liblog.FromKeeper(ctx, k).WithComponent("skyway-endblocker")
 	defer func() {
 		if r := recover(); r != nil {
@@ -42,6 +46,17 @@ func EndBlocker(ctx context.Context, k keeper.Keeper, cc *libcons.ConsensusCheck
 		if err != nil {
 			logger.WithError(err).Warn("Failed to prune attestations.")
 		}
+
+		if sdkCtx.BlockHeight()%updateValidatorNoncesPeriod == 0 {
+			// Update all validator nonces to the latest observed nonce, if
+			// suitable This makes sure validators don't get stuck waiting for
+			// events they can't get from the RPC, even though these events are
+			// already observed
+			err = k.UpdateValidatorNoncesToLatest(ctx, v)
+			if err != nil {
+				logger.WithError(err).Warn("Failed to update validator nonces.")
+			}
+		}
 	}
 
 	err = processGasEstimates(ctx, k, cc)

x/skyway/keeper/attestation.go

@@ -165,13 +165,6 @@ func (k Keeper) TryAttestation(ctx context.Context, att *types.Attestation) erro
 					return err
 				}
 
-				// Update all validator nonces to the claim nonce that was just
-				// processed
-				err = k.updateValidatorNoncesIfHigher(ctx, claim.GetChainReferenceId(), claim.GetSkywayNonce())
-				if err != nil {
-					return err
-				}
-
 				break
 			}
 		}

x/skyway/keeper/keeper.go

@@ -481,21 +481,26 @@ func (k Keeper) overrideNonce(ctx context.Context, chainReferenceId string, nonc
 	return nil
 }
 
-// updateValidatorNoncesIfHigher updates all validator nonces to `newNonce` only
-// if it is higher than the current record
-func (k Keeper) updateValidatorNoncesIfHigher(
+// UpdateValidatorNoncesToLatest updates all validator nonces to the last
+// observed skyway nonce only if it is higher than the current record
+func (k Keeper) UpdateValidatorNoncesToLatest(
 	ctx context.Context,
 	chainReferenceId string,
-	newNonce uint64,
 ) error {
 	logger := liblog.FromKeeper(ctx, k).WithComponent("update-validator-nonces-if-higher")
 
+	lastSkywayNonce, err := k.GetLastObservedSkywayNonce(ctx, chainReferenceId)
+	if err != nil {
+		logger.WithError(err).Warn("Failed to get last observed nonce.")
+		return err
+	}
+
 	store := k.GetStore(ctx, chainReferenceId)
 	prefixStore := prefix.NewStore(store, types.LastEventNonceByValidatorKey)
 
-	err := k.IterateValidatorLastEventNonces(ctx, chainReferenceId, func(key []byte, nonce uint64) bool {
-		if newNonce > nonce {
-			prefixStore.Set(key, types.UInt64Bytes(newNonce))
+	err = k.IterateValidatorLastEventNonces(ctx, chainReferenceId, func(key []byte, nonce uint64) bool {
+		if lastSkywayNonce > nonce {
+			prefixStore.Set(key, types.UInt64Bytes(lastSkywayNonce))
 		}
 
 		return false